"That's the trend in the women's game," said U.S. Fed Cup captain Mary Joe Fernandez of a year that will produce eight different major finalists. "If Serena's not playing well, it's wide open."

Which is to say, there are matches to play.

Despite a WTA-leading five titles, Williams has been so disappointed in her play this year — she failed to advance past the fourth round in three previous Slams — she has taken to sarcasm.

"It's so easy now because it's almost a joke for me because I have done little to no winning in the majors," the 32-year-old American said Wednesday after coming back to beat No. 11 seed Flavia Pennetta of Italy. "I think that definitely has been able to help me to relax, as well," she added.

Indeed, Williams has looked calm, focused and resolute. She has dropped the fewest games (22) and no sets in the Open.

But lefthander Makarova, seeded 17th, hasn't dropped a set either. And she already owns a Grand Slam win vs.Williams in the third round of the 2012 Australian Open.

Williams leads 3-1 in meetings, all on hardcourts, including a straight-sets victory earlier this year in Dubai, but the low-profile Makarova — she said she prefers to "stay in the shade" — is no pushover.

PHOTO GALLERY: SERENA'S ON-COURT STYLE

In 2004, Serena Williams took the court in this jean inspired ensemble at the U.S. Open. (Photo: Robert Deutsch, USA TODAY Sports)

Serena Williams is often photographed ay New York Fashion Week. On the court, her dresses also draw reviews. Here she plays Amelie Mauresmo at the U.S. Open in 2006. (Photo: Robert Deutsch USA TODAY Sports)

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Williams will have to stay on point, go for her serves, step into the court or risk being moved into uncomfortable positions by the fleet-footed Russian, who has few glaring weaknesses.

"I need to be a little bit more aggressive than she is; (make) her move definitely," said Makarova after defeating 2012-13 U.S. Open runner-up Victoria Azarenka in Wednesday's quarterfinals.

No. 10 seed Wozniacki, a two-time year-end No. 1, has rounded back into form this summer and will be a favorite when she faces off against 39th-ranked Peng, the biggest surprise of the tournament.

Peng will be the aggressor. With 21 aces, she trails only Williams (23) in the tournament. The Chinese player also will attempt to take the ball early and dictate off her double-fisted forehand and backhand as she did in dismantling quarterfinal opponent Belinda Bencic of Switzerland.

After struggling to find the right balance of offense and defense for much of the last two years, Wozniacki has been drawing errors with her movement and showing an ability to attack the net and open the court with her more dangerous backhand swing.

"It's definitely evolved," Wozniacki said of her game after routing No. 13 seed Sara Errani of Italy 6-0, 6-1 in her last match.

She will have experience on her side, too, having reached her only Grand Slam final here in 2009. Wozniacki dropped her first meeting with Peng in 2007 but has won the last five.

Still, on paper, there is little to argue.

"Serena has become the real heavy favorite to win," said Fernandez, who comments for ESPN. "She's determined. She's on a mission."